I can provide you with termination in mexico, and calling card services.
We also have a call shop software that works online for the end users of call shops (tarificador para casetas telefonicas) that works in conbination with a2billing.
We also have callback service in the city of Tijuana only, however if you are interested in callback in some other city that is no problem you would have to buy a did for the callback to have a callback number.
For example lets say you are an agent, and you have a customer that has an internet cafe and he needs call shop service, you as an agent can sell him service, and he can use the call shop online billing to bill his customers.
The did call back service in Tijuana is only for cell phones, the reason is technical Mexican phone companies Movistar, Telcel, and Unefon, do not provide the caller ID in the proper format, for example lets say you are in the USA and someone calls you using a cell phone by looking at the caller id alone you could not return the call easily since you would not know if it was a fixed or mobile number that called you.
And since cell phones have a larger market than fixed phones, the cid call back in tijuana is provided only for cell phones.
For low budget customers we also have shared dids, or regulars did for customers that what to purchase a did.
Check out the site
http://www.telefonostijuana.comLet me know if interested.